Lighting systems (such as headlights) are well-known and are used in a wide variety of applications, including automotive applications. In general, a lighting system includes one or more projector apparatus for emitting one or more distinct light patterns. For example, a lighting system may emit light in a low-beam pattern/mode in which light is generally emitted below the horizon. The lighting system may also emit light in a high beam pattern/mode in which light is generally emitted above and below the horizon.
Recent developments in headlamp performance ratings/testing procedures have changed the photometric output requirements, making it more difficult for manufactures to comply. Non-exhaustive examples of some potentially applicable regulations/testing procedures for glare in incoming traffic are described by United States National Highway Traffic Safety Administration (NHTSA) (e.g., at pages 96-99 and Table XIX-a of the Department of Transportation (DOT) 49 C.F.R. Parts 564 and 571 (which correspond to Vol. 72, No. 232 (Dec. 4, 2009) pages 68328-68331 of the Federal Register), hereinafter referred to as the NHTSA standard) as well as the Insurance Institute for Highway Safety (IIHS)™ Headlight Test and Rating Protocol (Version I) (February 2016). In general, the new requirements and/or testing procedures specify sharper gradient cutoffs, wider spreads, and reduced glare to oncoming traffic.
One way to produce a sharp gradient cutoff is through the use of a “projector” design headlamp. Projector headlamp designs involve light passing by a shutter (also referred to as a shade or shield) that blocks or subtracts light out of the pattern to produce a sharp gradient cutoff before passing the light to a projector lens. A shutter generates a low beam pattern. Some shutters are fixed (e.g., non-movable). Other shutters are movable and toggle between two positions that change the pattern from low beam to high beam by removing the blocking effect of the shutter. Examples of shutters in projector headlamps are seen in Pat. Pub. US 2009/0052200 (Tessnow) and U.S. Pat. No. 8,070,339 (Koike) at FIG. 7 therein described as prior art. Examples of other headlamps are shown in U.S. Pat. No. 9,150,144 (Abe); U.S. Pat. No. 9,068,710 (Lai); and U.S. Pat. No. 8,523,417 (Kobayashi).
A problem associated with the known shutter designs is that they can only block the light in specified areas; however, the known shutter designs cannot reduce the light in specified areas while still allowing some light to illuminate the area, because they are made of sheet metal (and are also heavy) in order to withstand the heat of a halogen or HID light source, as described for example in the treatise handbook Automotive Lighting and Human Vision, at Chapter 3.1, p. 107, Table 3.2 (Woerdenweber et al., Springer Verlag, Corp. 2007) (hereinafter “Automotive Lighting and Human Vision”). Put another way, the known shutter designs are an “all-or-nothing” design meaning they either allow all the available light to illuminate a specific area, or allow none of the available light to illuminate the specific area.